U.S. patent number 6,304,415 [Application Number 09/615,783] was granted by the patent office on 2001-10-16 for magnetic head.
This patent grant is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Michiko Hara, Akio Hori, Tadahiko Kobayashi, Takashi Koizumi, Tomohiko Nagata, Hiromi Sakata, Kohichi Tateyama, Hiroaki Yoda.
United States Patent |
6,304,415 |
Tateyama , et al. |
October 16, 2001 |
Magnetic head
Abstract
At least one magnetic pole out of a pair of magnetic poles is
provided with a T-shaped magnetic pole having a magnetic pole chip
at the position contacting with a magnetic gap and an auxiliary
magnetic pole which is wider than thereof. The proximity of an air
bearing surface of the T-shaped magnetic pole is composed of a
laminated film containing a magnetic material layer with a high
saturated magnetic flux density which composes the magnetic pole
chip and a portion of the auxiliary magnetic pole and a magnetic
material layer with a low saturated magnetic flux density which
composes the remaining portion of the auxiliary magnetic pole. When
the front portion of the magnetic pole with the track width of 1.8
.mu.m or less is composed of a laminated film containing a magnetic
material layer having a high saturated magnetic flux density and a
magnetic material layer having a low saturated magnetic flux
density, the thickness of the magnetic material layer having the
high saturated magnetic flux density is 0.5 .mu.m or more.
According to the above described magnetic pole, the magnetic
saturation near the tip portion of the magnetic pole is controlled,
so that preferable magnetic field strength and magnetic field
gradient can be attained when the track width is narrowed.
Inventors: |
Tateyama; Kohichi (Ichikawa,
JP), Yoda; Hiroaki (Kawasaki, JP),
Kobayashi; Tadahiko (Yokohama, JP), Sakata;
Hiromi (Kawasaki, JP), Hara; Michiko (Yokohama,
JP), Hori; Akio (Kawasaki, JP), Koizumi;
Takashi (Kawasaki, JP), Nagata; Tomohiko
(Yokohama, JP) |
Assignee: |
Kabushiki Kaisha Toshiba
(Kawasaki, JP)
|
Family
ID: |
26537157 |
Appl.
No.: |
09/615,783 |
Filed: |
July 13, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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150926 |
Sep 10, 1998 |
6108167 |
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Foreign Application Priority Data
|
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Sep 10, 1997 [JP] |
|
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9-245298 |
Sep 7, 1998 [JP] |
|
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10-253019 |
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Current U.S.
Class: |
360/125.43;
G9B/5.091; G9B/5.09; G9B/5.08; 360/122; 360/125.58; 360/125.6;
360/125.61 |
Current CPC
Class: |
G11B
5/3153 (20130101); G11B 5/3146 (20130101); G11B
5/3109 (20130101); G11B 5/3967 (20130101); G11B
5/3116 (20130101); G11B 5/3163 (20130101) |
Current International
Class: |
G11B
5/31 (20060101); G11B 5/39 (20060101); G11B
005/31 (); G11B 005/187 () |
Field of
Search: |
;360/119,120,126,122 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Tupper; Robert S.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier
& Neustadt, P.C.
Parent Case Text
This application is a division of application Ser. No. 09/150,926
filed on Sep. 10, 1998 U.S. Pat. No. 6,108,167.
Claims
What is claimed is:
1. A magnetic head comprising:
a magnetic gap positioned on an air bearing surface;
a pair of magnetic poles positioned to hold said magnetic gap
therebetween and at least one of which being composed of a T-shaped
magnetic pole having a magnetic pole chip contacting with said
magnetic gap and an auxiliary magnetic pole wider than said
magnetic pole chip; and
a coil positioned between said pair of magnetic poles to intersect
said magnetic poles,
wherein said T-shaped magnetic pole has a laminated film including
two or more kinds of magnetic material layers each having a
different saturated magnetic flux density, and a magnetic material
layer positioned at a side of said magnetic gap has higher
saturated magnetic flux density than the other magnetic material
layers, and forms the magnetic pole chip and a portion of the
auxiliary magnetic pole close thereto.
2. The magnetic head according to claim 1, wherein the width of a
contacting portion of the magnetic pole chip with said magnetic gap
is 1.8 .mu.m or less.
3. The magnetic head according to claim 1, wherein said T-shaped
magnetic head is provided with a first magnetic material layer
having a saturated magnetic flux density Bs.sub.1 and composing the
magnetic pole chip and the portion of the auxiliary magnetic pole
close thereto, and a second magnetic material layer having a
saturated magnetic flux density Bs.sub.2 which is lower than the
saturated magnetic flux density Bs.sub.1 and composing the
remaining portion of the auxiliary magnetic pole.
4. The magnetic head according to claim 3, wherein said T-shaped
magnetic head is further provided with a third magnetic material
layer having a saturated magnetic flux density Bs.sub.3 which is
higher than the saturated magnetic flux density Bs.sub.1 and being
positioned to contact with said magnetic gap.
5. The magnetic head according to claim 3, wherein the first
magnetic material layer and the second magnetic material layer
satisfy the relation; W.sub.1 /W.sub.0.gtoreq.Bs.sub.1 /Bs.sub.2,
wherein the width of the magnetic pole chip contacting with said
magnetic gap is defined as W.sub.0, and the width of the contacting
portion between the portion and the remaining portion of the
auxiliary magnetic pole is defined as W.sub.1.
6. The magnetic head according to claim 1, wherein the laminated
film contains a multi-layered film made of a magnetic layer and a
non-magnetic layer or a multi-layered film made of magnetic
layers.
7. The magnetic head according to claim 1, wherein said pair of
magnetic poles are respectively formed into the T-shaped magnetic
pole.
8. A magnetic head comprising:
a magnetic gap disposed on an air bearing surface;
a pair of magnetic poles disposed to hold the magnetic gap
therebetween and at least one of which being composed of a T-shaped
magnetic pole having a magnetic pole chip contacting with said
magnetic gap and an auxiliary magnetic pole wider than said
magnetic pole chip; and
a coil disposed between said pair of magnetic poles to intersect
the magnetic poles,
wherein the T-shaped magnetic pole has a laminated film including a
first magnetic material layer and a second magnetic material layer,
the first magnetic material layer has a saturated magnetic flux
density Bs.sub.1 and composes the magnetic pole chip and a portion
of the auxiliary magnetic pole close thereto, the second magnetic
material layer has a saturated magnetic flux density Bs.sub.2 which
is lower than the saturated magnetic flux density Bs.sub.1 and
composes the remaining portion of the auxiliary magnetic pole, and
the first magnetic material layer and the second magnetic material
layer satisfying the relation; W.sub.1 /W.sub.0.gtoreq.Bs.sub.1
/Bs.sub.2, wherein the width of the magnetic pole chip contacting
with said magnetic gap is defined as W.sub.0, and the width of the
contacting portion between the portion and the remaining portion of
the auxiliary magnetic pole is defined as W.sub.1.
9. A magnetic head comprising:
a pair of magnetic poles, one of the pair of magnetic poles having
a magnetic pole tip and an auxiliary magnetic pole, the magnetic
pole tip contacting a magnetic gap at an air bearing surface, the
auxiliary magnetic pole having a width in a track width direction
wider than a width of the magnetic pole tip in the track width
direction and including a first portion contacting with the
magnetic pole tip and a second portion disposed apart from the
magnetic tip, the one of the pair of magnetic poles having a first
layer of a first saturated magnetic flux density and a second layer
of a second saturated magnetic flux density which is lower than the
first saturated magnetic flux density, the first layer being
disposed in the magnetic pole tip and the first portion of the
auxiliary magnetic pole, and the second layer being disposed in the
second portion of the auxiliary magnetic pole;
the magnetic gap disposed between the pair of the magnetic poles at
the air bearing surface; and
a coil, a part of the coil being disposed between the pair of
magnetic poles.
10. A hard disk drive having a magnetic head, the magnetic head
comprising:
a magnetic gap positioned to be situated on an air bearing
surface;
a pair of magnetic poles positioned to hold said magnetic gap
therebetween and at least one of which being composed of a T-shaped
magnetic pole having a magnetic pole chip contacting with said
magnetic gap and an auxiliary magnetic pole wider than said
magnetic pole chip; and
a coil positioned between said pair of magnetic poles to intersect
said magnetic poles,
wherein said T-shaped magnetic pole has a laminated film including
two or more kinds of magnetic material layers each having a
different saturated magnetic flux density, and a magnetic material
layer which is positioned at a side of said magnetic gap and has
high saturated magnetic flux density out of the magnetic material
layers in laminated film, forming the magnetic pole chip and a
portion of the auxiliary magnetic pole close thereto.
11. A hard disk drive having a magnetic head, the magnetic head
comprising:
a magnetic gap disposed on an air bearing surface;
a pair of magnetic poles disposed to hold the magnetic gap
therebetween and at least one of which being composed of a T-shaped
magnetic pole having a magnetic pole chip contacting with said
magnetic gap and an auxiliary magnetic pole wider than said
magnetic pole chip; and
a coil disposed between said pair of magnetic poles to intersect
the magnetic poles,
wherein the T-shaped magnetic pole has a laminated film including a
first magnetic material layer and a second magnetic material layer,
the first magnetic material layer has a saturated magnetic flux
density Bs.sub.1 and composes the magnetic pole chip and a portion
of the auxiliary magnetic pole close thereto, the second magnetic
material layer has a saturated magnetic flux density Bs.sub.2 which
is lower than the saturated magnetic flux density Bs.sub.1 and
composes the remaining portion of the auxiliary magnetic pole, and
the first magnetic material layer and the second magnetic material
layer satisfying the relation; W.sub.1 /W.sub.0.gtoreq.Bs.sub.1
/Bs.sub.2, wherein the width of the magnetic pole chip contacting
with said magnetic gap is defined as W.sub.0, and the width of the
contacting portion between the portion and the remaining portion of
the auxiliary magnetic pole is defined as W.sub.1.
12. A hard disk drive having a magnetic head, the magnetic head
comprising:
a pair of magnetic poles, one of the pair of magnetic poles having
a magnetic pole tip and an auxiliary magnetic pole, the magnetic
pole tip contacting a magnetic gap at an air bearing surface, the
auxiliary magnetic pole having a width in a track width direction
wider than a width of the magnetic pole tip in the track width
direction and including a first portion contacting with the
magnetic pole tip and a second portion disposed apart from the
magnetic tip, the one of the pair of magnetic poles having a first
layer of a first saturated magnetic flux density and a second layer
of a second saturated magnetic flux density which is lower than the
first saturated magnetic flux density, the first layer being
disposed in the magnetic pole tip and the first portion of the
auxiliary magnetic pole, and the second layer being disposed in the
second portion of the auxiliary magnetic pole;
the magnetic gap disposed between the pair of the magnetic poles at
the air bearing surface; and
a coil, a part of the coil being disposed between the pair of
magnetic poles.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head in which
magnetic saturation is controlled at the tip portion when a track
thereof narrows.
2. Description of the Related Art
Recently, high densifying of magnetic recording density progresses.
For example, in HDD system, a system which is feasible to realize
the high recording density of 1 Gbpsi/inch.sup.2 becomes
commercially practical, and it is nevertheless required to densify
recording density. For achieving the high densifying of magnetic
recording, such technical challenges as make a recording track of a
thin-film magnetic head narrower in width, enlarge recording field
with the thus narrowed track, and make magnetic inclination steeper
in recording magnetic distribution in a line direction are remained
for the persons in the art.
FIG. 18 depicts a structure of a thin-film magnetic head as a
conventional and typical recording head. In FIG. 18, reference
numeral 1 indicates a lower magnetic pole. An upper magnetic pole 3
is formed over the lower magnetic pole 1 with a recording magnetic
gap 2 therebetween. The upper magnetic pole 3 has an air bearing
surface (ABS) which is shaped corresponding to the track width. The
upper magnetic pole 3 has a fan shape extending backward or to a
coil (not shown) from the proximity of the air bearing surface.
With the magnetic pole 3 having the shape shown in FIG. 18, the tip
portion corresponding to the narrowed track width is hardly
processed with high accuracy in the conventional manufacturing
process of heads. Furthermore, magnetic saturation occurs at a
narrow portion of the magnetic pole 3 (neck portion 4), so that it
is difficult to generate large recording magnetic field.
For increasing recording magnetic strength, the same structure as
that of the MIG (Metal In Gap) head which is used in a bulk head is
conducted experiments on the thin-film magnetic head. A thin-film
magnetic head provided with a magnetic material layer which has a
high saturated magnetic flux density with an extra-thin thickness
of about 0.2 .mu.m at a portion opposing to a magnetic gap is
particularly known. When the recording track width of the thin-film
magnetic head is narrowed, in a laminated film of two magnetic
material layers with different saturated magnetic flux densities,
the magnetic saturation occurs at the side of a lower saturated
magnetic flux density layer. Accordingly, not only recording
magnetic field strength decreases but also magnetic field
inclination reduces, thus losing resolution, so that a disadvantage
such as deterioration of NLTS (Non linear Transition Shift)
happens.
A T-shaped thin-film magnetic head shown in FIG. 19 is also
suggested to prevent magnetic saturation at a portion being
narrowed near the tip of a magnetic pole. The thin-film magnetic
head shown in FIG. 19 is provided, at the proximity of the air
bearing surface of at least one magnetic pole (upper magnetic pole
5 in FIG. 19), with a magnetic pole chip 5a contacting with the
recording magnetic gap 2 and an auxiliary magnetic pole 5b which is
wider than the magnetic pole chip in a state to have T-shaped
figure at the air bearing surface of the magnetic pole 5.
The T-shaped magnetic pole 5, as shown in FIG. 20, can be realized
by means of opening a trench 7 with a predetermined track width in
an insulation layer 6 formed on the recording magnetic gap 2 and
forming by embedding magnetic material layers in the trench 7. In
the T-shaped magnetic pole 5 using the trench 7, since the magnetic
pole 5a can be changed in the shape and the position thereof in
accordance with the shape of the trench, the magnetic pole chip 5a
with narrowed track can be accurately obtained.
However, when the surface width of the magnetic pole chip 5a
opposing to the gap is narrowed for ever-more narrowing of the
track width in the T-shaped magnetic pole 5, the magnetic
saturation occurs because of magnetic flux concentration at the
laminated portion (the contacting portion) between the magnetic
pole chip 5a and the auxiliary magnetic pole 5b. In this case,
disadvantages of decreasing recording magnetic field strength and
magnetic field inclination happen.
It is also investigated that the magnetic pole chip 5a in the
T-shaped magnetic pole 5 is made with magnetic materials having a
saturated magnetic flux density which is higher than that of the
auxiliary magnetic pole 5b. However, the troublesome magnetic
saturation at the laminated portion between the magnetic pole 5a
and the auxiliary magnetic pole 5b is not completely prevented with
the foregoing structure.
To be more specific, when the recording magnetic field is enlarged
to increase the recording magnetic field strength, the magnetic
saturation tends to break out at the laminated portion between the
magnetic pole chip 5a and the auxiliary magnetic pole 5b. If the
magnetic saturation occurs at the laminated portion, enough
electric current can not be sent into the magnetic pole chip 5a
made of the magnetic material having high saturated magnetic flux
density, so that the magnetic field strength can not be improved in
proportion to the increase of the recording current. Furthermore,
the magnetic gradient in the line direction lowers because of
magnetic field leaked out from portions where the magnetic
saturation occurs, then raising a deterioration in NLTS.
As described above, the conventional thin-film magnetic head
involves such disadvantage as tend to cause the magnetic saturation
at any portion in the head when narrowing. Since the magnetic
saturation in the magnetic head causes the recording magnetic field
strength and the magnetic field gradient to lower and further NLTS
to deteriorate, high densifying of the magnetic recording density
is prevented.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a
magnetic head which enables to control magnetic saturation at the
proximity of the front portion in a magnetic pole to obtain
excellent magnetic field strength and magnetic field gradient when
the recording width is narrowed.
A first magnetic head according to the present invention is
characterized by comprising a magnetic gap which is positioned to
be situated on an air bearing surface, a pair of magnetic poles
which are positioned to hold the magnetic gap therebetween and at
least one of which being composed of a T-shaped magnetic pole
having a magnetic pole chip contacting with the magnetic gap and an
auxiliary magnetic pole which is wider than the magnetic pole chip,
and a coil which is positioned between the pair of magnetic poles
to intersect the magnetic poles, wherein the T-shaped magnetic pole
has a laminated film including two or more kinds of magnetic
material layers each having a different saturated magnetic flux
density, and a magnetic material layer which is positioned at a
side of the magnetic gap and has high saturated magnetic density
out of the magnetic material layers in the laminated film,
composing the magnetic pole chip and a portion of the auxiliary
magnetic pole close thereto.
In the first magnetic head, not only the magnetic pole chip which
composes the tip portion in the magnetic pole but also a portion of
the auxiliary magnetic pole near the magnetic pole chip are
composed with a magnetic material layer having high saturated
magnetization. Accordingly, magnetic saturation is controlled at
the contacting portion between the magnetic pole chip with a narrow
width corresponding to the track width and the auxiliary magnetic
pole. By controlling magnetic saturation at the portion between the
magnetic pole chip and the auxiliary magnetic pole, preferable
recording magnetic field strength and magnetic field gradient can
be attained when the recording track is narrowed. Specifically,
when recording current is increased to raise recording magnetic
field strength, enough magnetic field strength can be attained
corresponding to the electric current, furthermore, steepness of
magnetic field gradient can be attained.
A second magnetic head according to the present invention is
characterized by comprising a magnetic gap which is positioned to
be situated an air bearing surface, a pair of magnetic poles which
are positioned to hold the magnetic gap, and a coil which is
positioned between the magnetic poles to intersect the magnetic
poles, wherein at least one magnetic pole out of the pair of
magnetic poles has the width at a the portion contacting with the
magnetic gap of 1.8 .mu.m or less and being composed of a laminated
film including two or more kinds of magnetic material layers each
having a different magnetic flux density at a proximity of the air
bearing surface, and the thickness of a magnetic material layer
having a high magnetic flux density positioned at a side of the
magnetic gap in the laminated film being 0.5 .mu.m or more.
A third magnetic head according to the present invention is
characterized by comprising a magnetic gap which is positioned to
be situated on the air bearing surface, a pair of magnetic poles
which are positioned to hold the magnetic gap therebetween, and a
coil which is positioned between the pair of magnetic poles to
intersect the magnetic poles, wherein at least one magnetic pole
out of the pair of magnetic poles is provided with a convex portion
having a shape with the width of the air bearing surface of 1.8
.mu.m or less and the height in the vertical direction to the air
bearing surface of 2 .mu.m or less and being composed of a
laminated film including two or more kinds of magnetic material
layers with different magnetic flux densities at a proximity of the
air bearing surface, and the thickness of the magnetic material
layer having a high saturated magnetic flux density positioned at a
side of the magnetic gap out of the laminated film being 0.5 .mu.m
or more.
In the second and the third magnetic heads according to the present
invention, the thickness of the magnetic material layer having a
high saturated magnetic flux density is 0.5 .mu.m or more, when the
recording track width is narrowed to 1.8 .mu.m or less. Namely,
since magnetic flux is rarely concentrated when the track width is
comparatively wide, magnetic gradient is increased by providing
magnetic material having a high saturated magnetic flux density
only at an extremely small area near a gap.
Comparing to this state, when the recording track width is narrowed
to 1.8 .mu.m or less, magnetic flux extremely concentrates and an
influence of magnetic saturation becomes great. Therefore, the
thickness of magnetic material layer having a high saturated
magnetic flux density is 0.5 .mu.m or more, so that preferable
recording magnetic field strength and magnetic field gradient can
be attained.
Specifically, as recognized from the third magnetic head, the air
bearing surface is formed with the convex portion with the width of
1.8 .mu.m or less and the height of 2 .mu.m or less, so that the
narrow track with the width of 1.8 .mu.m or less can be accurately
formed. At this time, since magnetic field strength extensively
decreases if the height in the vertical direction to the air
bearing surface is considerably high, the height of the convex
portion in the vertical direction to the air bearing surface should
be 2 .mu.m or less.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary view which shows the structure of the
principal portion in an embodiment of a magnetic
recording/reproducing separation head with a magnetic head
according to the present invention;
FIG. 2 is a view which shows a magnetic pole structure in the
proximity of an air bearing surface in the first embodiment of a
first thin-film magnetic head according to the present
invention;
FIG. 3 is a view showing a modification of the thin-film magnetic
head shown in FIG. 2;
FIG. 4 is a view showing another modification of the thin-film
magnetic head shown in FIG. 2;
FIG. 5 is a view which shows the magnetic pole structure in the
proximity of the air bearing surface in the second embodiment of
the first thin-film magnetic head according to the present
invention;
FIG. 6 is a view showing a modification of the magnetic pole
structure in the thin-film magnetic head shown in FIG. 2;
FIG. 7 is a view showing a modification of the magnetic pole
structure in the thin-film magnetic head shown in FIG. 5;
FIG. 8 is a view which shows the magnetic pole structure in the
proximity of the air bearing surface in the third embodiment of the
first thin-film magnetic head according to the present
invention;
FIG. 9 is a view which shows the magnetic pole structure in the
proximity of the air bearing surface in the fourth embodiment of
the first thin-film magnetic head according to the present
invention;
FIG. 10 is a view showing a modification of the magnetic pole
structure in the thin-film magnetic head shown in FIG. 8;
FIG. 11 is a view showing a modification of the magnetic pole
structure in the thin-film magnetic head shown in FIG. 9;
FIG. 12 is a view showing an example in which the magnetic pole
structure according to the present invention is applied to another
T-shaped magnetic pole;
FIG. 13 is a view showing another example in which the magnetic
pole structure according to the present invention is applied to
another T-shaped magnetic pole;
FIG. 14 is a perspective view which shows the composition of the
principal portion in an embodiment of a second thin-film magnetic
head according to the present invention;
FIG. 15 is a perspective view showing a modification of the
thin-film magnetic head shown in FIG. 14;
FIG. 16 is a perspective view which shows the structure of the
principal portion in an embodiment of a third thin-film magnetic
head according to the present invention;
FIG. 17 is a perspective view showing a modification of the
thin-film magnetic head shown in FIG. 16;
FIG. 18 is a view showing a magnetic pole structure in a
conventional and typical thin-film magnetic head;
FIG. 19 is a view showing a structure of T-shaped magnetic pole in
a conventional thin-film magnetic head; and
FIG. 20 is a view showing another structure of T-shaped magnetic
pole in a conventional thin-film magnetic head.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of the present invention will be described
below with reference to the attached drawings.
FIG. 1 is a fragmentary view which shows the structure of a
principal portion in an embodiment of a magnetic
recording/reproducing separation type head with a magnetic head
according to the present invention. In this drawing, reference
numeral 11 indicates a substrate. The substrate 11 is made, for
example, of an Al.sub.2 O.sub.3.TiC substrate having an Al.sub.2
O.sub.3 layer. On the substrate 11, formed is a lower side magnetic
shield layer 12 which is composed of a soft magnetic material such
as NiFe alloy or amorphus CoZrNb alloy with a thickness of 1 to 2
.mu.m or thereabouts.
On the lower side magnetic shield layer 12, a magneto-resistance
effect film (MR film) 14 is formed with a lower side reproducing
magnetic gap 13 thereunder which is composed of a non-magnetic
insulation material such as AlO.sub.x with a thickness of 150 mm or
thereabouts. With both edges of the MR film 14, connected are lead
electrodes 15 which respectively supply sense electric current to
the MR film 14. The MR film 14 and the lead electrodes 15 compose a
reproducing element portion.
On the MR film 14 and the lead electrodes 15, an upper side
magnetic shield layer 17 is formed with an upper side reproducing
magnetic gap 16 thereunder which is composed of the same
non-magnetic insulation material as that for the lower side
reproducing magnetic gap 13. The upper side shield layer 17 is
composed of the same soft magnetic material as that of the lower
side magnetic shield layer 12. With the above explained component
elements, a shield type MR head 18 is composed as a reproducing
head.
On the shield type MR head 18 described above, a thin-film magnetic
head 19 is provided as a recording head. A lower recording magnetic
pole of the thin-film magnetic head 19 is composed of the same
magnetic layer as the upper side magnetic shield layer 17. Namely,
the upper side magnetic shield layer 17 of the shield type MR head
18 also serves as the lower recording magnetic pole for the
thin-film magnetic head 19. On the lower recording magnetic pole 17
also serving as the upper side magnetic shield layer, provided is a
recording magnetic gap 20 which is composed of a non-magnetic
insulation material such as AlO.sub.x.
An upper recording magnetic pole 21 is provided on the recording
magnetic gap 20. The upper recording magnetic pole 21 of which a
proximity of Air Bearing Surface (ABS) is composed of a magnetic
pole chip 21a and an wider auxiliary magnetic pole 21b than that of
the chip 21a, the details thereof being described later. The
auxiliary magnetic pole 21b is extended backward from a laminated
portion with the upper magnetic pole chip 21a. Coils 22 composed of
Cu or the like are provided under the upper auxiliary magnetic pole
21b. In other words, the coils 22 are arranged between the upper
auxiliary magnetic pole 21b and the lower recording magnetic pole
17. The coils 22 are embedded in an insulation layer such as
polyimide which is not shown. As has described above, the principal
part of the thin-film magnetic head 19 as a recording head is
composed of these component elements.
Next, the portion fronting on and being close to media of the
recording magnetic poles 17, 21 will be described with reference to
FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8, FIG. 9,
FIG. 10, and FIG. 11.
The upper recording magnetic pole 21 of which the proximity of the
ABS is provided, for example as shown in FIG. 2, with the magnetic
pole chip 21a which is positioned at the side of the recording
magnetic gap 20 and the auxiliary magnetic pole 21b which is
situated on the magnetic pole chip 21a. The magnetic pole chip 21a
touches the recording magnetic pole gap 20 with a predetermined
track width W.sub.0. The auxiliary magnetic pole 21b is
dimensionally wide compared with that of the magnetic pole chip
21a. The magnetic pole chip 21a and the auxiliary magnetic pole 21b
compose a T-shaped magnetic pole.
The above described upper recording magnetic pole 21 formed into T
is composed of a laminated film which contains two or more kinds of
magnetic material layers each having different saturated magnetic
flux density at least at the proximity of ABS. The upper recording
magnetic pole 21 has a laminated film containing a first magnetic
material layer 23 having a saturated magnetic flux density
Bs.sub.1, and a second magnetic material layer 24 having a
saturated magnetic flux density Bs.sub.2 which is lower than the
saturated magnetic flux density Bs.sub.1 (Bs.sub.2
<Bs.sub.1).
It should be understood that the first and the second magnetic
material layers 23, 24 are adapted to keep a combination in which
the first magnetic material layer 23 shows a higher saturated
magnetic flux density than that of the second magnetic material
layer 24. The first magnetic material layer 23 is made of a
magnetic material with a high saturated magnetic flux density (High
Bs magnetic material) such as Ni.sub.50 Fe.sub.50 alloy, CoFe
alloy, iron nitride based material, and the like. In this case, the
second magnetic material layer 24 can optionally employ permalloy
(Ni.sub.80 Fe.sub.20 and the like), amorphous CoFeZr alloy, sendust
or the like which respectively has comparatively low saturated
magnetic flux density. When satisfying a relation of Bs.sub.1
>Bs.sub.2, other combinations, besides the above explained
combination, can be applied.
The first magnetic material layer 23 showing a high saturated
magnetic flux density can be altered with a muti-layered film 27
with a first magnetic film 25 and a second magnetic film 26 as
shown in FIG. 3, or a multi-layered film 29 with a magnetic film 25
and a non-magnetic film 28 as shown in FIG. 4. The multi-layered
films 27, 29 are available to be composed with various combinations
of materials. It is more recommended to employ a combination in
which a magnetic character such as a high saturated magnetic
density, a high permeability can be obtained, and a combination in
which electric resistance becomes stronger to control eddy current
loss.
The multi-layered film 27 can employ such combination as ferric
alloy and amorphous alloy such as CoZrNb or substances each having
different crystalline diameter. The thus mentioned multi-layered
film 27 attains fine-grain state of magnetic particle, which
contributes an improvement in soft magnetic characteristics. The
multi-layered film 29 can employ such combination as ferric alloy
and electrical insulator like SiO.sub.x. The thus explained
multi-layered film 29 attains a high electrical resistance state,
which contributes a reduction of an eddy currents loss.
Incidentally, the multi-layered films 27, 29 can be appropriated
for the second magnetic material layer 24.
In the laminated film with the first magnetic material layer 23 and
the second magnetic material layer 24, the first magnetic material
layer 23 having a high saturated magnetic flux density forms the
upper magnetic pole chip 21a and a part of the upper auxiliary
magnetic pole 21b near the upper magnetic pole chip 21a. In
concrete, the upper magnetic pole chip 21a and a bottom portion of
the upper auxiliary magnetic pole 21b having a thickness of 0.3
.mu.m or thereabouts is formed of the first magnetic material layer
23. The remaining portion of the upper auxiliary magnetic pole 21b
with a thickness of 3 .mu.m or thereabouts is composed of the
second magnetic material layer 24.
The high Bs material layer (a part of the first magnetic material
layer 23 ) corresponding to the bottom portion of the upper
auxiliary magnetic pole 21b proves an improved effect of magnetic
gradient when the thickness thereof is considerably thick. When the
thickness of the high Bs material layer is extremely thin, the
magnetic saturation can not be prevented. Accordingly, the bottom
portion of the upper auxiliary magnetic pole 21b in the first
magnetic material layer 23 is preferable to have a thickness of 0.1
.mu.m to 0.5 .mu.m or thereabouts.
The magnetic pole structure shown in FIG. 2 obtains the follow. At
the first step, the upper magnetic pole chip 21a is formed by
embedding with the high Bs material (first magnetic material 23)
inside a trench 31 opened in an insulation layer 30 composed of
SiO.sub.x and the like by means of the spatter method. After
smoothing an upper surface corresponding to the upper magnetic pole
chip 21a, the high Bs material layer (First magnetic material layer
23) is further laminated to an extent corresponding to the bottom
part of the upper auxiliary magnetic pole 21b. Next, a low Bs
material layer (Second magnetic material layer 24) is formed.
The upper auxiliary magnetic pole 21b can be provided by patterning
by means of such as a standard PEP (Photo Engravement Process).
Alternatively, the upper auxiliary magnetic pole 21b can be formed
by patterning in accordance with the form of the upper auxiliary
magnetic pole 21b after the first magnetic material layer 23 is
continuously laminated from the upper magnetic pole chip 21a to the
portion corresponding to the bottom portion of the upper auxiliary
magnetic pole 21b and the second magnetic material layer 24 is
further formed thereon.
As shown in FIG. 2, the portion in the upper auxiliary magnetic
pole 21b composed of the first magnetic material layer 23 need not
to be uniformly provided to form on the bottom surface portion of
the upper auxiliary magnetic pole 21b. For example, as shown in
FIG. 5, the first magnetic material layer 23 can be formed into a
shape projecting from the upper magnetic pole chip 21a toward the
upper auxiliary magnetic pole 21b. The structure described above
can be realized by applying, for example, a plating process to
obtain the upper magnetic pole chip 21a with the first magnetic
material layer 23 with high Bs materials.
Namely, when the upper magnetic material pole chip 21a is provided
with the first magnetic material layer 23 by means of the plating
process, the first magnetic material layer 23 is finished to have a
form rising upward from the upper magnetic pole 21a. The rising
portion can be used as a part of the upper auxiliary magnetic pole
21b. Next, the second magnetic material layer 24 is further
laminated and patterned into a form in conformity with the upper
auxiliary magnetic pole 21b to obtain the magnetic pole structure
shown in FIG. 5.
Reviewing the upper recording magnetic pole 21 as the T-shaped
magnetic pole shown in FIG. 2 and FIG. 5, the width W.sub.1
corresponding to the touching portion, where a portion of the upper
auxiliary magnetic pole 21b composed of the first magnetic material
layer 23 contacts with the remaining portion of the upper auxiliary
magnetic pole 21b composed of the second magnetic material layer
24, is recommended to be set wider than the track width W.sub.0 (a
contacting width between the magnetic pole chip 21a and the
recording magnetic gap 20) in accordance with a ratio of a
saturated magnetic flux density of the first magnetic material
layer 23 and that of the second magnetic material layer 24.
Namely, a proportion of the width W.sub.1 of the contacting portion
and the track width W.sub.0 is recommended to be set, in accordance
with the saturated magnetic flux density Bs.sub.1 of the first
magnetic material layer 23 and the saturated magnetic flux density
Bs.sub.2 of the second magnetic material layer 24, that is, to
satisfy a relation; W.sub.1 /W.sub.0.gtoreq.Bs.sub.1 /Bs.sub.2. The
ratio of W.sub.1 and W.sub.0 (W.sub.1 /W.sub.0) is set to be larger
than the ratio of saturated magnetic flux densities (Bs.sub.1
/Bs.sub.2), so that recording current with which only a portion
opposing to a gap of the upper magnetic pole chip 21a is
magnetically saturated can be sent without magnetic saturation at
the laminated portion of the first magnetic material layer 23 and
the second magnetic material layer 24.
As described above, the high Bs first magnetic material layer 23 is
appropriated not only for the upper magnetic pole chip 21a but also
for a part of the bottom portion in the upper auxiliary magnetic
pole 21b, and the remaining portion of the upper auxiliary magnetic
pole 21b is further formed thereon with the low Bs second magnetic
material layer 24, so that magnetic saturation can be controlled at
the contacting portion between the upper portion magnetic pole chip
21a with the narrow width corresponding to the track width W.sub.0
and the upper auxiliary magnetic pole 21b. Accordingly, even if the
track width further narrows, excellent recording magnetic field
strength and magnetic field gradient can be attained. The above
described effect is specifically remarkable when the recording
track width W.sub.0 narrows to 1.8 .mu.m or less.
Furthermore, in a thin-film magnetic head having the recording
track W.sub.0 width of 1.8 .mu.m or less, when recording current is
increased to gain recording magnetic field strength, the magnetic
field strength can be correspondingly raised, therefore more
preferable magnetic field gradient can be attained. Namely, a
thin-film magnetic head 19 as a recording head having excellent
magnetic field strength and magnetic field gradient can be
realized.
The high Bs first magnetic material layer 23 composing a portion of
the upper auxiliary magnetic pole 21b provides advantages in
control of the magnetic saturation at a corner portion of the upper
auxiliary magnetic pole 21b. Accordingly, undesired recording
because of leaked magnetic field from the corner portion can be
prevented. If all the portions of the upper auxiliary magnetic pole
are composed of the low Bs soft magnetic layer as the conventional
T-shaped magnetic pole, the magnetic saturation occurs at the
corner portion of the upper auxiliary magnetic pole to thereby
arise undesired recording at needless area because of the leaked
magnetic field from the corner portion.
Moreover, the conventional recording head needs to be shortened in
length of depth (throat height) of the air bearing surface of the
recording magnetic gap when the track width narrows. The width of
the upper portion auxiliary magnetic pole 21b is set wider instead
to prevent magnetic saturation at the contacting portion, so that
enough magnetic flux is supplied to the magnetic pole chip 21a
through the auxiliary magnetic pole 21b. Consequently, throat
height can be lengthened.
For example, when the upper recording magnetic pole 21 shown in
FIG. 2 and FIG. 5 provided with the recording head having the
throat height of 5 .mu.m is used to record on the magnetic
recording media having the coercive force of .about.21000e, the
over-light characteristics reaches 38 dB to generate enough
recording magnetic field. In the conventional recording head, since
the over-light characteristics considerably depends on the throat
height, when integrated with the MR reproducing component or the
GRM reproducing component of which reproducing output also
considerably depend on the stripe height, a run-in processing
margin of ABS surface extremely becomes small because of
disalignment between the throat height end and the stripe height
end. The thin-film magnetic head according to the present invention
has the throat height margin by an order of several .mu.m, thus
improving the manufacturing yield.
The magnetic pole structure shown in FIG. 2 and FIG. 5 is the
preferable example in which the proximity of the air bearing
surface of the upper recording magnetic pole 21 is composed of a
two-layered laminated film containing the high Bs first magnetic
material layer 23 and the low Bs second magnetic material layer 24.
The proximity of the air bearing surface of the upper recording
magnetic pole 21 is, as shown in FIG. 6 and FIG. 7, able to be
composed of a laminated film including three or more magnetic
material layers.
Now, the magnetic pole shown in FIG. 6 and FIG. 7 is provided with
a third magnetic material layer 32, which shows further higher
saturated magnetic flux density Bs.sub.3 than that of the first
magnetic material layer 23 (Bs.sub.3 >Bs.sub.1), at the
extremity of the upper magnetic pole chip 21a, that is the portion
in the upper magnetic pole chip 21a contacting with the recording
magnetic gap 20. The third magnetic material layer 32 can be made
of iron nitride materials such as FeZrN or FeN with the thickness
of 0.2 .mu.m or thereabouts.
Namely, the proximity of the air bearing surface of the upper
recording magnetic pole 21 is formed from a laminated film
containing the third magnetic material layer 32 having the highest
saturated magnetic flux density Bs.sub.3, the first magnetic
material layer 23 made of the high Bs material (Bs.sub.1), and the
second magnetic material layer 24 made of the low Bs material
(Bs.sub.2). These magnetic material layers 32, 23, and 24 can be
formed under a combination of various magnetic materials in which
each saturated magnetic flux density satisfies the relation,
Bs.sub.3 >Bs.sub.1 >Bs.sub.2. When the above described
magnetic pole is applied, the magnetic field strength further
increases and the magnetic field gradient becomes steeper.
In the foregoing embodiment, the example, in which only the upper
recording magnetic pole 21 is intentionally formed as the T-shaped
magnetic pole, is described, the lower recording magnetic pole 17
opposing to the upper recording magnetic pole 21 with the recording
magnetic gap 20 therebetween, as shown in FIG. 8 and FIG. 9, can be
formed as the T-shaped magnetic pole which is lifted toward the
recording magnetic gap 20, too. The lower recording magnetic pole
17 having a lower magnetic pole chip 17a which is raised upward and
a corresponding lower auxiliary magnetic pole 17b which is wider
than that of the chip 17a can be obtained, for example, by trimming
0.5 .mu.m or thereabouts off the lower recording magnetic pole 17
remaining the section corresponding to the track width.
When the magnetic pole structure shown in FIG. 8 and FIG. 9 is
applied, the recording magnetic field in the track width direction
becomes steeper to be more preferable to record with the narrowed
track. In the lower recording magnetic pole 17, it is preferable
that the lower magnetic pole chip 17a and a portion of the lower
auxiliary magnetic pole 17b close thereto are composed of the high
Bs first magnetic material layer 23, and the remaining portion of
the lower auxiliary magnetic pole 17b is composed of the low Bs
second magnetic material layer 24. Furthermore, as shown in FIG. 10
and FIG. 11, only the portions of the lower magnetic pole chip 17a
and the upper magnetic pole chip 21a respectively contacting with
the recording magnetic gap 20 can be provided with a third magnetic
material layer 32 having a further higher saturated magnetic flux
density than that of the first magnetic material layer 23.
The above explained relation between the ratio of the contacting
width of the magnetic pole chip 21a and the auxiliary magnetic pole
21b and the track width, and the ratio of the saturated magnetic
flux densities between the first magnetic material layer 23 and the
second magnetic material layer 24 is effective in the standard
T-shaped magnetic pole.
Namely, in the magnetic structure shown in FIG. 12, the proximity
of the air bearing surface of the upper recording magnetic pole 21
is provided with the magnetic pole chip 21a which contacts with the
recording magnetic gap 20 with the predetermined track width
W.sub.0 and, the auxiliary magnetic pole 21b which is positioned
above the magnetic pole chip 21a and wider than the width
W.sub.0.
The upper magnetic pole chip 21a is formed of the first magnetic
material layer 23 made of magnetic material having a high saturated
magnetic flux density, for example Ni.sub.50 Fe.sub.50 alloy or the
like. The upper auxiliary magnetic pole 21b is formed of the second
magnetic material layer 24 made of permalloy (Ni.sub.80 Fe.sub.20
or the like), amorphous CoFeZr alloy or the like having a
comparatively low saturated magnetic flux density. The proximity of
the ABS of the upper recording magnetic pole 21 is composed of
these laminated film. The component materials for the first
magnetic material layer 23 and the second magnetic material layer
24 are the same as those in the aforementioned embodiment.
The width W.sub.2 of the upper magnetic pole chip 21a contacting
with the upper auxiliary magnetic pole 21b is set wider than the
track width W.sub.0 (the width contacting with the recording
magnetic gap 20) in accordance with the ratio of the saturated
magnetic flux densities of the first magnetic material layer 23 and
the second magnetic material layer 24. That is to satisfy the
relation, W.sub.2 /W.sub.0.gtoreq.Bs.sub.1 /Bs.sub.2.
The above explained magnetic pole shape can be obtained by the
steps of the following. At the first step to obtain it, the angle
of the side walls of a trench 31 is adjusted with the etching
conditions to form the trench 31 in an insulation layer 30 made of
SiO.sub.x or the like by means of the PEP and the chemical dry
etching. Next, the high Bs first magnetic material layer 23 is
formed by embedding in the trench 31 by means of the spatter method
or the like.
As explained above, by setting the ratio of the respective width of
the upper magnetic pole chip 21a (W.sub.21 /W.sub.0) wider than the
ratio of the saturated magnetic flux densities (Bs.sub.1
/Bs.sub.2), the magnetic saturation can be prevented at the
contacting portion between the upper magnetic pole chip 21a and the
upper auxiliary magnetic pole 21b (the laminated portion) even if
recording current, with which the portion of the upper magnetic
pole chip 21a opposing to the gap is magnetically saturated, is
passed. Therefore, lowering of magnetic field strength and
deterioration of magnetic gradient can be controlled.
For example, when the first magnetic material layer 23 is made of
Ni.sub.50 Fe.sub.50 alloy having a saturated magnetic flux density
of 1.57T and the second magnetic material layer 24 is made of
amorphous CoFeZr alloy having a saturated magnetic flux density of
1.2T, the width (the track width) W.sub.0 of the upper magnetic
pole chip 21a opposing to the recording magnetic gap 20 is set in
1.2 .mu.m. In this case, the width W.sub.2 of the upper magnetic
pole chip 21a contacting with the upper auxiliary magnetic pole
21b, that is the width of the joint portion of the T-shaped
magnetic pole, is set in more than 1.2.times.(1.5/1.2)=1.5 .mu.m.
Thus, the magnetic saturation can be prevented at the contacting
portion between the upper magnetic pole chip 21a and the upper
auxiliary magnetic pole 21b (the laminated portion) even if
recording current, with which the portion of the upper magnetic
pole chip 21a opposing to the gap is magnetically saturated, is
passed. Consequently, the thin-film magnetic head showing
preferable magnetic field strength and magnetic field gradient can
be realized.
In the above described thin-film magnetic head, as shown in FIG.
13, the lower recording magnetic pole 17 can be formed as the
T-shaped magnetic pole which is lifted toward the recording
magnetic gap 20, too. Furthermore, in the lower recording magnetic
pole 17, the lower magnetic pole chip 17a is recommended to be made
of the high Bs first magnetic material layer 23 and the lower
auxiliary magnetic pole 17b is also recommended to be made of the
low Bs second magnetic material layer 24, and the width W.sub.3 of
the lower magnetic pole chip 17a contacting with the lower
auxiliary magnetic pole 17b is recommended to be set wider than the
width W.sub.0 occupying a contacting portion with the recording
magnetic gap 20 in accordance with the ratio of the saturated
magnetic flux densities (Bs.sub.1 /Bs.sub.2). Namely, it is
preferable to satisfy the relation, W.sub.3
/W.sub.0.gtoreq.Bs.sub.1 /Bs.sub.2.
In the above explained embodiment, the T-shaped magnetic pole
structure according to the present invention is mainly applied in
the trench pall structure to be formed by embedding the magnetic
material in the trench, however, the thin-film magnetic head
structure in the scope of the present invention is not limited to
this structure. The magnetic head according to the present
invention can be applied to, for example, the notch structure
taught in Japanese Patent Laid-open Application No. Hei 7-296328,
and to the structure by embedding a magnetic pole tip portion into
a structure formed in advance described in the U.S. Pat. No.
5,283,942.
The T-shaped magnetic pole is superior on the magnetic gradient
compared with other magnetic poles which will be described later,
since employing a narrowed structure toward the vicinity of the
magnetic gap. The proximity of the air bearing surface in the
T-shaped magnetic pole is optionally available to be formed with
the high Bs magnetic material layer until the uppermost portion of
the auxiliary magnetic pole.
Next, an embodiment of a second magnetic head according to the
present invention will be described in reference to FIG. 14 and
FIG. 15. FIG. 14 is a perspective view which shows the composition
of the principal portion in an embodiment of the second magnetic
head according to the present invention. FIG. 14 only shows the
principal portion of the thin-film magnetic head as a recording
head. The whole structure of the thin-film magnetic head in this
embodiment, and the whole structure of a magnetic
recording/reproducing separation head using the same are the same
as those in FIG. 1.
The thin-film magnetic head shown in FIG. 14 is provided with a
lower magnetic pole (lower recording magnetic pole) 41, a magnetic
gap (recording magnetic gap) 42 formed thereon, and an upper
magnetic pole (upper recording magnetic pole) 43 further formed
thereon. The lower magnetic pole 41 and the magnetic gap 42 are
made of the same materials as described above.
The upper magnetic pole 43 is composed of a laminated film
including two or more kinds of magnetic material layers each having
a different saturated magnetic flux density at least at the
proximity of the air bearing surface. In concrete, the upper
magnetic pole 43 is provided with a laminated film 44 containing a
first magnetic material layer 45 having the saturated magnetic flux
density Bs.sub.1 and a second magnetic material layer 46 having the
saturated magnetic flux density Bs.sub.2 which is lower than the
saturated magnetic flux density Bs.sub.1 (Bs.sub.2
<Bs.sub.1).
The first and the second magnetic material layers 45, 46 can be
formed under a combination of magnetic materials as those in the
above explained embodiment. Furthermore, the high Bs first magnetic
material layer 45 can be made of a multi-layered film having
various magnetic material layers as shown in FIG. 3, or a
multi-layered film including a magnetic layer and a non-magnetic
layer as shown in FIG. 4. The combination of these materials for
the multi-layered films is also the same as the above instance. The
second magnetic material layer 46 can employ a multi-layered
film.
The proximity of the air bearing surface of the upper magnetic pole
43 composed of a laminated film 44 which contains the first
magnetic material layer 45 and the second magnetic material layer
46 is formed into a shape corresponding to the recording track
width W.sub.0 by means of the FIB (Focused Ion Beam) process from
the laminating direction. Namely, the width of the air bearing
surface of the laminated film 44 is defined to correspond to the
track width W.sub.0, and the high Bs first magnetic material layer
45 positioned at the side of the magnetic gap 42 makes contact with
the magnetic gap 42 with the track width W.sub.0.
The thin-film magnetic head in this embodiment is narrowed in the
track width W.sub.0 of 1.8 .mu.m or less. Since the tip portion of
the thin-film magnetic head is processed by means of the FIB, the
upper magnetic pole 43 corresponding to the recording track width
W.sub.0 of 1.8 .mu.m or less can be accurately obtained. The tip
portion of the upper magnetic pole 43 can be naturally processed by
the standard PEP process, in which it is preferable to use a light
with a short wavelength for exposure at the time of the PEP to
improve the processing accuracy.
The thickness t of the high Bs first magnetic material layer 45 is
0.5 .mu.m or more to make the recording track width W.sub.0
correspond to the magnetic head with the narrowed to 1.8 .mu.m or
less. In other words, with the conventional magnetic head with
comparatively wide track width, the magnetic flux rarely
concentrates, so that the very small area near the gap is provided
with the high Bs magnetic material to increase magnetic field
gradient.
If the recording track width W.sub.0 is narrowed to 1.8 .mu.m or
less, the magnetic flux extremely concentrates, then an influence
of magnetic saturation becomes great. Therefore, in the second
magnetic head according to the present invention, the thickness of
the high Bs first magnetic material layer 45 is set in more than
0.5 .mu.m. Accordingly, preferable recording magnetic field
strength and magnetic field gradient can be attained. However, if
the thickness of the high Bs first magnetic material layer 45 is
considerably thick, the improved effect in magnetic field gradient
detracts, so that the thickness of the first magnetic material
layer 45 is recommended to be set in less than 2.0 .mu.m.
Reviewing in the case of the narrowing the recording track width
W.sub.0 less than 1.8 .mu.m, by making the thickness t of the high
Bs first magnetic material layer 45 of 0.51 .mu.m or more, the
magnetic saturation can be controlled at the laminated portion of
the first magnetic material layer 45 and the second magnetic
material layer 46 in the tip portion of the upper magnetic pole 43
corresponding to the track width W.sub.0. Accordingly, when the
recording track width W.sub.0 is 1.8 .mu.m or less, preferable
recording magnetic field strength and magnetic field gradient can
be realized.
The relation between magnetic field strength and magnetic field
gradient when the recording track width W.sub.0 and the thickness t
of the high Bs first magnetic material layer 45 are changed is
shown in Table 1. Here, the first magnetic material layer 45 is
made of Ni.sub.50 Fe.sub.50 with the saturated magnetic flux
density Bs.sub.1 of 1.4 T and the second magnetic material layer 46
is made of Ni.sub.80 Fe.sub.20 with the saturated magnetic flux
density of 0.9 T.
TABLE 1 Thickness t of first magnetic material layer 45 0.3 .mu.m
1.0 .mu.m Magnetic Magnetic Magnetic Magnetic field field field
field strength gradient strength gradient Track 1 .mu.m .times.
.times. .largecircle. .largecircle. width W.sub.0 2 .mu.m
.largecircle. .largecircle. .largecircle. .times.
As shown in Table 1, it is understandable that when the recording
track width is comparatively wide, by making the thickness t of the
high Bs first magnetic material layer 45 thin, preferable magnetic
field strength and magnetic field gradient can be attained.
Contrary, when the recording track is narrowed, by making the
thickness t of the high Bs first magnetic material layer 45 thick,
preferable magnetic field strength and magnetic field gradient can
be realized.
As shown in FIG. 6 and FIG. 7, the proximity of the air bearing
surface of-the upper magnetic pole 43 can be composed of a
laminated film including three or more magnetic material layers.
Namely, the proximity of the air bearing surface of the upper
magnetic pole 43 can be composed of a laminated film containing the
third magnetic material layer having the highest saturated magnetic
flux density Bs.sub.3, the first magnetic material layer made of
the high Bs material (Bs.sub.1), and the second magnetic material
layer made of the low Bs material (Bs.sub.2). In this case, the
combination of the magnetic materials is preferable to be the same
as the above described embodiment. With this magnetic pole, the
magnetic field strength can be further increased and the magnetic
field gradient can be steeper.
In the above explained embodiment, the example, in which only the
tip portion of the upper magnetic pole 43 is modified into the
shape corresponding to the recording track width W.sub.0, is
described, and the portion 41a of the lower magnetic pole 41
contacting with the magnetic gap 42 can be modified into the same
shape, too. In this case, by masking the tip portion of the upper
magnetic pole 43 in the lower magnetic pole 41, the portion (41a)
can be processed simultaneously with the upper magnetic pole 43 as
a mask. With this magnetic pole structure, steepness of recording
magnetic field in the track width direction is increased to be
further advantageous for recording with the narrowed track.
Incidentally, the lower magnetic pole 41 is also recommended to be
composed of the high Bs first magnetic material layer and the low
Bs second magnetic material layer. Furthermore, only the portion of
the lower magnetic pole 41 contacting with the magnetic gap 42 may
be formed with the third magnetic material layer showing a
saturated magnetic flux density which is further higher than that
of the first magnetic material layer.
Next, embodiments of a third magnetic head according to the present
invention will be described in reference to FIG. 16 and FIG. 17.
FIG. 16 is a perspective view which shows the composition of the
principal portion in an embodiment of the third magnetic head
according to the present invention. FIG. 16 shows only the
principal portion of the thin-film magnetic head as a recording
head. The whole structure of the thin-film magnetic head in this
embodiment, and the whole structure when applying the same to a
magnetic recording/reproducing separation head are the same as
those in FIG. 1.
The thin-film magnetic head shown in FIG. 16 is provided with a
lower magnetic pole (lower recording magnetic pole) 51, a magnetic
gap (recording magnetic gap) 52, and an upper magnetic pole (upper
recording magnetic pole) 53 as the poles being formed one on the
other in this order. The lower magnetic pole 51 and the magnetic
gap 52 are made of the same materials as the above explained
embodiments.
The upper magnetic pole 53 is composed of a laminated film which
includes two or more kinds of magnetic material layers each having
a different saturated magnetic flux density. As can be seen from
the drawing, the upper magnetic pole 53 has a laminated film 54
containing a first magnetic material layer 55 having the saturated
magnetic flux density Bs.sub.1 and a second magnetic material layer
56 having the saturated magnetic flux density Bs.sub.2 which is
lower than the saturated magnetic density Bs.sub.1 (Bs.sub.2
<Bs.sub.1).
It should be understood that the first and the second magnetic
material layers 55, 56 can be formed under the same combination of
the magnetic materials as those in the above explained embodiments.
Furthermore, the high Bs first magnetic material layer 55 can be
obtained from a multi-layered film made of various magnetic layers
as shown in FIG. 3, or a multi-layered film made of a magnetic
layer and a non-magnetic layer as shown in FIG. 4. The combination
of the materials for the multi-layered film is also the same as
above. The second magnetic material layer 56 can be altered with a
multi-layered film.
The proximity of the air bearing surface of the upper magnetic pole
53 composed of the laminated film 54 containing the first magnetic
material layer 55 and the second magnetic material layer 56 is
provided with a convex portion 53 a having a shape with the width
W.sub.0 of 1.8 .mu.m or less and the height h in the vertical
direction to the ABS of 2 .mu.m or less by means of, for example,
the FIB process from the air bearing surface. The ABS is formed by
the convex portion 53a.
The convex portion composing the tip portion of the upper magnetic
pole 53 has a shape projecting toward the ABS. The first magnetic
material layer 55 composing the convex portion 53a contacts with
the magnetic gap 52 at the ABS with the track width W.sub.0. The
height h of the convex portion 53a in the direction of the ABS is 2
.mu.m or less. In the case of that the track width is defined at
W.sub.0 less than 1.8 .mu.m, if the height h of the convex portion
53a exceeds 2 .mu.m, the recording magnetic field strength
extensively decreases.
The thin-film magnetic head in the embodiment is narrowed in the
track width W.sub.0 of 1.8 .mu.m or less. The tip portion of the
thin-film magnetic head is processed by means of the FIB from the
air bearing surface to form the tip of the upper magnetic pole 53
into the convex portion 53a, so that the upper magnetic pole 53
corresponding to the recording track width W.sub.0 of 1.8 .mu.m or
less can be accurately obtained. The convex portion 53a of the
upper magnetic pole 53 can be naturally processed by the standard
PEP process, in which it is preferable to use a light with a short
wavelength for exposure at the time of the PEP to improve the
processing accuracy.
The thickness t of the high Bs first magnetic material layer 55 is
0.5 .mu.m or more to make the recording track width W.sub.0
correspond to the magnetic head having the narrowed track of 1.8
.mu.m or less. When the recording track width W.sub.0 is narrowed
to 1.8 .mu.m or less, the magnetic flux extremely concentrates, so
that an influence of magnetic saturation becomes great. Therefore,
in the third magnetic head according to the present invention, the
thickness of the high Bs first magnetic material layer 55 is 0.5
.mu.m or more. Accordingly, preferable recording magnetic field
strength and magnetic field gradient can be attained. However,
since the thickness of the high Bs first magnetic material layer 55
is considerably thick, the improved effect in magnetic gradient is
detracted, so that the thickness of the first magnetic material
layer 55 is recommended to be set in less than 20 .mu.m.
Reviewing in the case of the narrowing the recording track width
W.sub.0 of 1.8 .mu.m or less, by making the thickness t of the high
Bs first magnetic material layer 55 of 0.5 .mu.m or more, the
magnetic saturation can be controlled at the laminated portion of
the first magnetic material layer 55 and the second magnetic
material layer 56 in the convex portion 53a corresponding to the
track width W.sub.0. Accordingly, when the recording track width
W.sub.0 is set in less than 1.8 .mu.m, preferable recording
magnetic field strength and magnetic field gradient can be
realized.
As shown in FIG. 6 and FIG. 7, the proximity of the air bearing
surface of the upper magnetic pole 53 can be composed of a
laminated film including three or more magnetic material layers.
Namely, the proximity of the air bearing surface of the upper
magnetic pole 53 can be composed of a laminated film which contains
the third magnetic material layer having the highest saturated
magnetic flux density Bs.sub.3, the first magnetic material layer
made of the high Bs material (Bs.sub.1), and the second magnetic
material layer made of the low Bs material (Bs.sub.2). In this
case, the combination of the magnetic materials is preferable to be
the same as the above explained embodiments. With this magnetic
pole described above, the magnetic field strength can be further
increased and the magnetic field gradient can be steeper.
In the above explained embodiment, the instance, in which only the
tip portion of the upper magnetic pole 53 is modified into the
convex portion 53a corresponding to the recording track width
W.sub.0, is described, and, as shown in FIG. 17, the tip of the
lower magnetic pole 51 can be modified into the same as the convex
portion 51a. In this case, the lower magnetic pole 51 can be
processed simultaneously with the upper magnetic pole 53. According
to this magnetic pole structure, steepness of recording magnetic
field in the track width direction is increased to be further
advantageous for recording with the narrowed track.
Incidentally, the lower magnetic pole 51 is also recommended to be
composed of the high Bs first magnetic material layer and the low
Bs second magnetic material layer. Furthermore, only the portion of
the lower magnetic pole 51 contacting with the magnetic gap 52 may
be formed with the third magnetic material layer showing a
saturated magnetic flux density which is higher than that of the
first magnetic material layer.
As has been recognized in the above explained embodiments,
according to the magnetic head of the present invention, magnetic
saturation can be controlled when narrowing the track width.
Consequently, when the track is narrowed, preferable magnetic field
strength and magnetic field gradient can be attained. Accordingly,
it is possible to provide the magnetic head suitable for high
densifying of the magnetic recording density.
* * * * *